Device and method for optically inspecting operating holes formed in heads of screws

ABSTRACT

Detection of defective operating holes formed in the heads of screws with heads is carried out by inserting a dummy bit to measure the depth of the hole. But this method is inefficient. Thus, it is desired to make it possible to inspect defective or non-defective by image inspection. The inspection device includes an inspecting portion for positioning and holding a screw with a head with the head up, a CCD camera provided right over the inspecting portion, an annular light source arranged between the inspecting portion and the CCD camera, and a determining device for processing an image of the CCD camera and determining whether defective or non-defective based on the processed image. The operating hole of the screw is illuminated by the annular light source so that no shadow forms to vividly photograph the hole bottom of the operating hole with the CCD camera. It is also possible to inspect the top surface of the head of a screw.

BACKGROUND OF THE INVENTION

[0001] This invention relates to an inspection device and method for optically inspecting operating holes formed in heads of screws having a head (among screws having a head referred to in this invention, bolts having an operating hole are included) or the heads' top surfaces, and a method for detecting that chipping has developed in the punch of a header for working the heads of screws by use of the inspection device.

[0002] Screws with a head are inspected for necessary items after manufacture and delivered after removing defectives. Among the inspection items, there is inspection of operating holes formed in the heads of screws. Among the operating holes of screws, there are hexagonal, Torx, square, cross, plus-minus, which is a combination of cross and minus, HIOS (trade name) and special-shaped holes.

[0003] Operating holes are simultaneously formed when screw heads are formed by a header. If there is minute chipping at the tip of a portion of the punch of the header for forming operating holes, it is transferred to the bottom of a hole, so that the bottom will partially bulge. Further, after working of operating holes by the header has been normally done, foreign matter produced due e.g. to working of threads may enter the hole and the foreign matter may be fixed to and remain in the bottom of the hole when the threads have been plated with the foreign matter stuck to the bottom of the hole. In this case too, the bottom of the hole will bulge.

[0004] If such defects develop, an operating bit cannot be properly received in the operating hole, so that there may arise trouble in the operation of the screw, or the hole may be crushed due to forcible operation. Thus, the inspection of such an operating hole has heretofore been carried out by inserting a dummy bit to confirm the depth of such a hole.

[0005] Inspection by a dummy bit has a problem in the treating capacity and the cost is high too. Therefore, we thought of employing an efficient image inspection method. But with a conventional image inspection device, if inspection areas are limited to central portions of operating holes, inspection is possible. But it was impossible to inspect the more important portions where defects tend to develop.

[0006] Defects of operating holes tend to develop not at the central portions of the holes but at the outer peripheral portions. For example, since the above-described chipping of the header develops at the outer peripheral edge at the tip of the punch, defects of operating holes due to this chipping naturally develop at the outer peripheral portions of the holes.

[0007] If trials are made to inspect the outer peripheral portions of the operating holes, where these defects concentrate, with an existing inspection device, shades form at the edge portions on the outer periphery of the operating holes, so that it is difficult to see the difference of recesses and protrusions of the hole bottoms from images of the camera. Since defects are protrusions, it is necessary to see the recesses and protrusions of the hole bottoms for image inspection. Since this was impossible, there was no other way but to employ an inefficient method of confirming the depth with a dummy bit.

[0008] Therefore, an object of this invention is to make it possible to detect defects of operating holes with image inspection to improve the inspection efficiency.

SUMMARY OF THE INVENTION

[0009] According to this invention, there is provided a method of inspecting screws having heads comprising positioning and holding a screw with a head to be inspected with its head facing a CCD camera in an inspecting portion, throwing illuminating light from an annular light source arranged on the side of the inspecting station nearer to the CCD camera to surround the view field of the camera on the head of the screw with the head, photographing the top of the head of said screw, which is arranged in the inspecting portion with said camera in this state, processing the image obtained, and determining whether an operating hole formed in the head of said screw or the top surface of the head is defective or non-defective based on information after processing, and an inspection device for screws having heads comprising an inspecting portion for positioning and holding a screw with a head to be inspected with its head facing a CCD camera, the CCD camera, which opposes the head of the screw that has been held in said inspecting portion, an annular light source arranged between said inspecting portion and said CCD camera to surround the view field of the CCD camera, and a determining device for processing an image of the CCD camera and determining between defective and non-defective based on the processed image, wherein the top of the screw is photographed by said CCD camera while throwing light from said annular light source from the obliquely forward direction on the head of the screw that has been placed in the inspecting portion, and an image obtained is processed to determine in said determining device whether an operating hole formed in the head of the screw or the top surface of the head is defective or non-defective.

[0010] There is also provided a method of detecting chipping of a punch of a header for forming heads of screws wherein inspection of operating holes or top surfaces of screws with heads that are fed from a head forming step is conducted using the above inspection method or inspection device, and if there are defects in inspection areas set on each operating hole or top surface and detection of defects in identical inspection areas have been made continuously for a plurality of screws, determination is made that chipping has developed in the punch of the header.

[0011] The inspection device may further comprises a turntable for receiving screws with heads to be inspected in cutout grooves formed along its outer periphery at constant pitches with their heads facing upward, and transporting the screws with the heads that have been received in said cutout grooves to the inspecting portion by turning it with a vertical shaft as a fulcrum, and dispensing portion for sorting the screws with heads on which determination has been made whether defective or non-defective into defectives and non-defectives and taking them out of said cutout grooves.

[0012] The inspection device may further comprises a turntable having radially extending grooves provided on its top surface along the outer periphery at constant pitches to receive screws with heads to be inspected so that they are horizontal with their heads on the outer peripheral side to deliver the screws with the heads that have been received in said grooves to the inspecting portion by turning it, and dispensing portion for sorting the screws with heads on which determination has been made whether defective or non-defective into defectives and non-defectives and taking them out of said cutout grooves.

[0013] Preferably, the annular light source of the inspection device has its center arranged on the line connecting the center of the inspecting portion and the center of the CCD camera.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which:

[0015]FIG. 1 is an entire schematic view of the inspection device of this invention;

[0016]FIG. 2 is a plan view schematically showing a sorter in which the device of FIG. 1 is mounted;

[0017]FIG. 3A is an explanatory view of the illuminating principle by the inspection device of this invention;

[0018]FIG. 3B is a view showing an illuminating state of an operating hole on an enlarged scale;

[0019]FIG. 4A is a view showing an image of a normal operating hole captured by a CCD camera;

[0020]FIG. 4B is a view showing an image of an abnormal operating hole captured by the CCD camera;

[0021]FIG. 5A is a side view of a Torx screw showing with its head cut away;

[0022]FIG. 5B is a plan view of the head of the Torx screw;

[0023]FIG. 6 is a view showing an example of a production system for screws with heads;

[0024]FIG. 7A is an entire schematic sectional view of another embodiment of the inspection device; and

[0025]FIG. 7B is a perspective view of grooves formed in a turntable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026]FIGS. 1 and 2 show an embodiment of the inspection device of this invention. It includes an inspecting portion 1 for positioning and holding a screw W having a head to be inspected, a CCD camera 2 arranged right over the inspecting portion 1, an annular light source 3 arranged between the inspecting portion 1 and the CCD camera 2, and a determining device 4 for carrying out determination as to defective and non-defective of operating holes by processing images photographed by the CCD camera 2. The inspection device 10 comprises these four elements.

[0027] The inspection device 10 is mounted in e.g. a sorter 13 of FIG. 2, which uses a turntable 5. In the sorter 13 of FIG. 2, in the outer periphery of the turntable 5, which is rotated with a vertical shaft 5 b as a fulcrum, cutout grooves 5 a into which shanks of screws W having heads (hereinafter merely mentioned as screws W) are inserted, are formed at regular pitches. At a supply portion 6, screws W are introduced into the cutout grooves 5 a. The heads of the screws W are supported on the top surface of the table 5. In this state, the table 5 is turned intermittently or continuously to feed screws W to an inspecting portion 7 for carrying out inspection of the lengths of shanks of the screws or the inspecting portion 1 for carrying out inspection as to defective or non-defective of operating holes with the inspection device 10 of FIG. 1 (the number of inspecting portions of the sorter can be increased or reduced as necessary).

[0028] Screws W that has passed the final inspecting portion are sorted into defectives and non-defectives and taken out of the turntable 5 at a dispensing portion. In FIG. 2, 9 is a guide plate for closing the inlets of the cutout grooves 5 a in the range from the supply portion 6 to the dispensing portion 8 in order to prevent a fall of screws W. The dispensing means at the dispensing portion 8 is not limited to illustrated actuators 8 a. It is also possible to dispense them by blowing air.

[0029] The CCD camera 2 photographs the head of a screw W brought into the inspecting portion 1 from right over it.

[0030] Further, the illustrated annular light source 3 is formed by providing numerous light emitting diodes (LEDs) 3 b on the underside of a ring 3 a. If the annular light source 3 has its center placed on or near the line connecting the center of the inspecting portion 1 and the center of the CCD camera 2, it is possible to uniformly throw light on the inspecting portion 1 from all areas in the circumferential direction.

[0031]FIG. 3 schematically shows how illuminating light L is thrown on the head of a screw W placed in the inspecting portion 1 from the annular light source 3. 2 a in the figure shows a lens of the CCD camera 2. In the case of illumination using a point light source, depending on the depth of an operating hole A formed in the head of a screw W or the light projecting angle, there are portions where illuminating light L is interrupted by the edge of the operating hole A and does not reach the hole bottom (hatched portion in FIG. 3), so that a shadow forms at this portion. But using the annular light source, the portion where the shadow forms is illuminated brightly by the light from the opposite direction, so that no shadow forms. Thus, the hole bottom vividly appears on the camera image. Further, since the illuminating light is thrown obliquely relative to the hole bottom from above, if there are defects (protrusions) on the hole bottom, shadows due to the defects will form there.

[0032]FIG. 4A shows an image of a normal operating hole A captured by the CCD camera 2. FIG. 4B shows an image of an operating hole A in which chipping has developed on the punch of the header and defects B due to the chipping have developed on the hole bottom. The defects B that have appeared on the image of FIG. 4B are displaced to the outer peripheral side of the operating hole A, so that recesses and protrusions are formed. To the position of the defects B, while light emitted from the side where there are the defects B scarcely reaches, light from the other side reaches without being interrupted. Thus, shadows that are not seen on the image of a normal operating hole form at the portions where the defects have developed. Thus, according to existence or non-existence of such shadows, it is possible to determine whether the hole bottom is defective or non-defective, i.e. whether the operating hole A is defective or non-defective.

[0033] The determining means 4 has an image processing portion for subjecting images photographed by the CCD camera 2 to binalizing processing. Further, it has the functions of setting inspection areas a enclosed in circles in FIG. 4B, and the function of determining whether the inspection areas a have any defects from the processed images.

[0034] The operating hole A shown in FIG. 3 is an operating hole of a Torx screw shown in FIG. 5 and has six grooves with which protrusions of an operating bit engage. Possibility is high that defects of the operating hole A develop at groove portions. Thus, by setting inspection areas at the positions enclosed in the circles in FIG. 4B, it is possible to reliably find such defects and reject them.

[0035] With the inspection device of this invention, it is possible to carry out determination on defective or non-defective of an operating hole formed in the head of a screw by image inspection as described above, and thus it is possible to markedly improve the inspection efficiency. For example, in continuous inspection using the sorter of FIG. 2, compared with manual operation carried out using a dummy bit, the number of screws processed was about three times for Torx screws and about six times for cross screws.

[0036] Further, if the inspection device of this invention is arranged in a manufacturing line for screws with heads for determination on defective or non-defective of operating holes at the heads of screws delivered one after another from the head forming step, it is possible to quickly find that chipping has developed on the punch of the header for forming heads of screws.

[0037] Since the punch of the header controls the stroke, it is possible to find a large chipping accompanying change in stroke. But minute chipping that will not influence the stroke cannot be confirmed while the header is operating. If the header is operated at a high speed until such confirmation is made, defectives will be produced in large amounts, which is not preferable.

[0038] Thus, the inspection device of this invention is used. If there are defects in the inspection areas set for each operating hole, and defects are detected for a plurality of screws at the same inspection area, one can presume that chipping has developed in the header punch. Thus, by this method, it is possible to find chipping early. To screws immediately after working heads with a header, machining oil is stuck. Thus, if image inspection of operating holes is carried out with the device of this invention immediately after passing the header, inspection is preferably carried out after blowing machining oil and foreign matter stuck on the hole bottom using e.g. air.

[0039]FIG. 6 shows an example of the production control system for screws with heads. It includes a manufacturing device 12 for screws with heads that is installed in a plant, a sorter 13 of products including the inspection device of this invention, a packaging belt conveyor 14, a personal computer 15 provided in an office of the manufacturing plant, a personal computer 16 provided in the head office of the manufacturer, and a personal computer 17 for controlling the sorter in a company for carrying out maintenance of the sorter 13.

[0040] The manufacturing devices 12 cut materials to a predetermined length, form heads with a header, form threads, etc. Also, the sorter 13 carries out inspection on defective and non-defective for the screws with a head and sorts them into defectives and non-defectives.

[0041] The manufacturing devices 12 and the sorter 13 are connected to the personal computer 15 through a LAN network 18 in the company. Further, the personal computers 15 and 16 are adapted to exchange information through the Internet network. By the personal computers 15 and 16, the production state, stock state and the like are comprehensively controlled. Further, salesmen can access the personal computer at the head office using notebook personal computers or PDAs to know the production state and stock state.

[0042] In such a production system, it is possible to quickly detect chipping of the punch of the header from defects developed in the operating holes of screws produced. It is also possible to detect any other trouble such as stoppage of the device. Thus, it is possible to notify a device operator of the trouble through e.g. the cell phone 19.

[0043] Here, description was made using a Torx screw as an example. But the device of this invention can be used for inspection of screws having hexagonal, square, cross, plus-minus, HIOS, and special-shaped holes, and inspection on defective or non-defective of the top surface of the head of a screw. Screws of which the heads are to be inspected may or may not have operating holes.

[0044] Inspection of screws may be carried out after plating.

[0045] Further, the inspection of screws can be carried out with screws W to be inspected held horizontal as shown in FIG. 7. The inspection device of FIG. 7 has a turntable 25 having radially extending grooves 25 a provided at the outer peripheral portion of the top surface at constant pitches in the circumferential direction. The grooves 25 a are preferably V-grooves as shown.

[0046] Screws W to be inspected are dropped into the grooves 25 a on the top surface of the turntable 25 so as to be horizontal and with their heads on the outer peripheral side. Then, by turning the turntable 25 with a vertical shaft 25 b as a fulcrum, the screws W held by the turntable 25 are fed into the inspecting portion 1.

[0047] The inspecting portion 1, the CCD camera 2, which faces the head of a screw W, and the annular light source 3, which is arranged between the CCD camera 2 and the turntable 25, are arranged on a horizontal centerline C. In this device too, inspection can be carried out in the same manner as with the inspection device of FIG. 2.

[0048] The carrier means for screws for inspection with screws W horizontal is not limited to the illustrated turntable 25. For example, parallelly arranged V-grooves or the like may be formed on the carrier surface of an endless transportation path of a conveyor device as represented by a belt conveyor, and screws may be held in the grooves for inspection of the heads of the screws during transportation.

[0049] In the inspection device and inspection method of this invention, the annular light source is arranged between the inspecting portion and the CCD camera, and illumination of the head of a screw with the head arranged in the inspecting portion is carried out with illuminating light from the annular light source. By using the annular light source, since light is thrown on a portion shaded by illumination of the point light source from the opposite side, no shadow forms at an edge portion on the outer periphery of the operating hole.

[0050] Further, since the illuminating light from the annular light source is introduced obliquely into the operating hole from above, if there is any deficiency in the form of a protrusion, a shadow due to the protrusion forms, so that recesses and protrusions on the hole bottom appear vividly on camera images. Thus, it is possible to conduct image inspection of operating holes, which dramatically improves inspection efficiency.

[0051] The inspection device of this invention can also be used for the inspection on defective or non-defective of the top surface of the head of a screw. Further, by using the inspection method or inspection device of this invention, chipping that has developed in the punch of the header for forming heads of screws can be found quickly based on the inspection state of operating holes or the top surfaces of heads. Detailed description on the method therefor is made in the next chapter. 

1. A method of inspecting screws having a head comprising the steps of positioning and holding a screw with a head to be inspected with its head facing a CCD camera in an inspecting portion, throwing illuminating light on the head of the screw with the head from an annular light source arranged on the side of the inspecting station nearer to the CCD camera so as to surround the view field of the CCD camera, photographing the head of said screw, which is arranged in the inspecting portion with said camera in this state, processing the image obtained, and determining whether an operating hole formed in the head of said screw or the top surface of the head is defective or non-defective based on information after processing.
 2. An inspection device for screws having a head comprising a CCD camera, an inspecting portion for positioning and holding a screw with a head to be inspected with its head facing said CCD camera, which opposes the head of the screw held in said inspecting portion, an annular light source arranged between said inspecting portion and said CCD camera so as to surround the view field of said CCD camera, and a determining device for processing an image of said CCD camera and determining between defective and non-defective based on the processed image, wherein the top of the screw is photographed by said CCD camera while throwing light from said annular light source from obliquely forward direction on the head of the screw that has been placed in said inspecting portion, and an image obtained is processed in said determining device to determine whether an operating hole formed in the head of the screw or the top surface of the head is defective or non-defective.
 3. An inspection device for screws with a head as claimed in claim 2 further comprising a turntable for receiving screws with a head to be inspected in cutout grooves formed along its outer periphery at constant pitches with their heads facing upward, and transporting the screws with a head that have been received in said cutout grooves to said inspecting portion by turning it around a vertical shaft, and dispensing portion for sorting the screws with a head on which determination has been made into defectives and non-defectives and taking them out of said cutout grooves.
 4. An inspection device for screws with a head as claimed in claim 2 further comprising a turntable having radially extending grooves provided on its top surface along the outer periphery at constant pitches to receive screws with a head to be inspected so that they are horizontal with their heads on the outer peripheral side to deliver the screws with the heads that have been received in said grooves to said inspecting portion by turning it, and dispensing portion for sorting the screws with a head on which determination has been made into defectives and non-defectives and taking them out of said cutout grooves.
 5. A method of detecting chipping of a punch of a header for forming heads of screws wherein inspection of operating holes or top surfaces of screws with a head that are fed from a head forming step is conducted using the inspection device claimed in claim 2, and if there are defects in inspection areas set on each operating hole or top surface and detection of defects in identical inspection areas have been made continuously for a plurality of screws, determination is made that chipping has developed in the punch of the header.
 6. A method of detecting chipping of a punch of a header for forming heads of screws wherein inspection of operating holes or top surfaces of screws with a head that are fed from a head forming step is conducted using the inspection device claimed in claim 3, and if there are defects in inspection areas set on each operating hole or top surface and detection of defects in identical inspection areas have been made continuously for a plurality of screws, determination is made that chipping has developed in the punch of the header.
 7. A method of detecting chipping of a punch of a header for forming heads of screws wherein inspection of operating holes or top surfaces of screws with a head that are fed from a head forming step is conducted using the inspection device claimed in claim 4, and if there are defects in inspection areas set on each operating hole or top surface and detection of defects in identical inspection areas have been made continuously for a plurality of screws, determination is made that chipping has developed in the punch of the header. 